Don't freeze input strings

See 34321e4a433bb7eef48fd743286601403f8f7d82 for background on
ImmutableString vs String.

Our String type cannot delegate typecasting to ImmutableString, because
the latter freezes its input: duplicating the value after that gives us
an unfrozen result, but still mutates the originally passed object.

1 files changed, 11 insertions, 2 deletions

diff --git a/activemodel/test/cases/type/string_test.rb b/activemodel/test/cases/type/string_test.rb
index 222083817e..47d412e27e 100644
--- a/activemodel/test/cases/type/string_test.rb
+++ b/activemodel/test/cases/type/string_test.rb
@@ -12,16 +12,25 @@ module ActiveModel
       end
 
       test "cast strings are mutable" do
-        s = "foo"
         type = Type::String.new
+
+        s = "foo"
         assert_equal false, type.cast(s).frozen?
+        assert_equal false, s.frozen?
+
+        f = "foo".freeze
+        assert_equal false, type.cast(f).frozen?
+        assert_equal true, f.frozen?
       end
 
       test "values are duped coming out" do
-        s = "foo"
         type = Type::String.new
+
+        s = "foo"
         assert_not_same s, type.cast(s)
+        assert_equal s, type.cast(s)
         assert_not_same s, type.deserialize(s)
+        assert_equal s, type.deserialize(s)
       end
     end
   end